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Int J Med Microbiol. 2014 Jul;304(5-6):662-8. doi: 10.1016/j.ijmm.2014.04.015. Epub 2014 May 9.

Haemophilus influenzae stores and distributes hemin by using protein E.

Author information

1
Medical Microbiology, Department of Laboratory Medicine Malmö, Lund University, SE-205 02 Malmö, Sweden.
2
Protein Chemistry, Department of Laboratory Medicine Malmö, Lund University, SE-205 02 Malmö, Sweden.
3
Section of Clinical and Experimental Infectious Medicine, Department of Clinical Sciences, Lund University, SE-221 84 Lund, Sweden.
4
Department of Biochemistry and Structural Biology, Lund University, SE-221 00 Lund, Sweden.
5
Medical Microbiology, Department of Laboratory Medicine Malmö, Lund University, SE-205 02 Malmö, Sweden. Electronic address: kristian.riesbeck@med.lu.se.

Abstract

The human pathogen Haemophilus influenzae causes mainly respiratory tract infections such as acute otitis media in children and exacerbations in patients with chronic obstructive pulmonary disease. We recently revealed the crystal structure of H. influenzeae protein E (PE), a multifunctional adhesin that is involved in direct interactions with lung epithelial cells and host proteins. Based upon the PE structure we here suggest a hypothetical binding pocket that is compatible in size with a hemin molecule. An H. influenzae mutant devoid of PE bound significantly less hemin in comparison to the PE-expressing wild type counterpart. In addition, E. coli expressing PE at the surface resulted in a hemin-binding phenotype. An interaction between hemin and recombinant soluble PE was also demonstrated by native-PAGE and UV-visible spectrophotometry. Surface plasmon resonance revealed an affinity (Kd) of 1.6 × 10(-6)M for the hemin-PE interaction. Importantly, hemin that was bound to PE at the H. influenzae surface, was donated to co-cultured luciferase-expressing H. influenzae that were starved of hemin. When hemin is bound to PE it thus may serve as a storage pool for H. influenzae. To our knowledge this is the first report showing that H. influenzae can share hemin via a surface-located outer membrane protein.

KEYWORDS:

Haemophilus influenzae; Hemin; Protein E

PMID:
24863527
DOI:
10.1016/j.ijmm.2014.04.015
[Indexed for MEDLINE]

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